When truck is first started, cold or warm, voltage is just under 12 volts and can drop to 10. After about half a minute it goes to normal at around 13+. Idle has fluctuation with volts too. But idle speed is different, it drops 50 or so RPM just like when the AC kicks on, only the AC is off. I just replaced the CPS.

Any Ideas?

 

That is the grid heater kicking in.

 

I am relatively new to running a diesel, but I thought the grid heater would only kick in when the engine was cold?

 

I am thinking if the wait to start light is lit, the grid heaters will activate. Does the voltage fluctuation stop after a short period?

 

Yes, after running for a few minutes. I never seem to have any time to sit and wait until the fluctuation stops,, but I guess it stops while driving. I do wait for the "wait" light to go out before starting.

 

Everything sounds normal.

 

I thought this might be the case, but need to hear it from someone else. Better to be safe than stranded!

Thanx for your help Robert78.5